1. Technical Field
This invention relates to a method and apparatus for detecting a moving target and, more specifically, to a method and apparatus for detecting a moving target within a cluttered background.
2. Discussion
In certain image processing systems it is necessary to acquire a target which is moving against a cluttered background. In particular, certain applications require that the target must be detected and acquired autonomously. Typically the requirements on such acquisition systems are such that the probability of a missed detection or a false detection is extremely low. The satisfaction of these performance requirements implies a reasonably high signal to noise ratio and a method to substantially suppress the background clutter. The present invention primarily addresses methods of clutter suppression.
One method of detecting a moving object and isolating it from background clutter is disclosed in U.S. patent application, Ser. No. 07/229,390, (now U.S. Pat. No. 4,937,878) filed 8/8/88 herein incorporated by reference. That application discloses an image processing acquisition system in which an image of the object is generated by first generating a difference between a current image frame and an image frame taken at a previous time, and second, generating a difference between the current image frame and another previous image frame. This subtraction procedure eliminates some of the background clutter since the background scene of the three image frames is nearly the same. The two difference image frames are then logically ANDed such that only the current position of the object of interest is detected.
A second method of detecting a moving object within a scene having background clutter is disclosed in U.S. patent application Ser. No. 07/229,196, herein incorporated by reference. In that application, the image frames, including the object of interest, of three consecutively taken images are correlated together. A median value for each pixel position of the correlated image frames is then selected, and each median pixel value is subtracted from the pixel value of one of the image frames to form a difference image. A threshold intensity value is determined for each pixel position. The threshold intensity values are then applied to the difference image such that the pixels exceeding the threshold value are associated with the object of interest.
Although these two systems described above have met with favorable success, there is still room for improving the performance of these types of acquisition systems. It is therefore an object of this invention to provide a moving target detection method and apparatus incorporating an increase in performance and accuracy over the above-described systems, and further, decrease the acquisition time, utilize less hardware, and reduce the amount of clutter leakage.